172 THE PHYSIOLOGY OF PLANTS 



The separation of the rooted portions . should take place at 

 the usual time of transplanting. 



In the previously mentioned method of propagation by 

 portions of roots with adventitious buds, as e.g. in Rhus, 

 JEsculus macrostachya, and others, the production of buds on 

 the . roots can be fostered by continual pruning in of the 

 mother-plant and by injuring the roots. But such wild stock 

 produced from root buds is not so good for grafting upon as 

 seedlings, as it has a great tendency to produce more adven- 

 titious buds, and therefore to weaken the main stem. 



§ 35. What rules should be followed in striking cuttings. 



A cutting is a portion of a plant detached from the parent 

 stock, and which becomes an independent plant by the forma- 

 tion of new roots. The new roots take their origin either 

 immediately at the cut end or at some little distance from the 

 latter. In different plants the power of producing adventitious 

 roots is very diflFerent. Speaking generally, we may say that 

 the older the various organs of a plant are, the less inclined they 

 are to form adventitious roots, and that of the various cultivated 

 plants those are least able to be propagated by cuttings which 

 have a hard and brittle wood. Of our fruit-trees, apples and 

 pears very readily form a strong protective callus over a cut, 

 but do not easily produce adventitious roots. 



Prom the Paradise stock cuttings can readily be struck, 

 however. The same may be said of the Myrobalan plum, 

 Quince, Vine, and Ribes. Of other trees, soft-wooded Poplars, 

 Willows, Ailmithus, Platanus, and Paulownia readily produce 

 roots, while Rdbinia, Elms, Beeches, Oaks, Walnuts are not 

 to do so. 



If a cutting is to form roots, and therefore to develop new 

 organs, it must contain a suflncient supply of plastic matter for 

 that purpose. This material has either been formed in a 

 previous vegetative period and is stored up in the shoot (woody 

 cuttings), or the cutting must be able to form the necessary 

 substances after it has been detached from the parent plant 

 (herbaceous cuttings). The latter must therefore always be 



